The present invention relates to the diagnostics used for revealing possible component faults in a vehicle, particularly a motor vehicle.
In particular, the invention relates to a method for diagnosing a possible fault of a component of a vehicle comprising a step of storing a distance traveled by the vehicle at a time when an event associated with the fault occurs.
In the case of motor vehicles in particular, the engines are conventionally provided with computers making it possible to help with management of the components.
As an example, the computer may control an injection system, an automatic gearbox, etc.
It is also known that such a computer may also be used in the context of the aforementioned diagnosis.
It will be noted as a preliminary that usually a diagnosis made by the vehicle is called an onboard diagnosis.
In particular this involves running tests based in particular on measurements and detecting possible defective operation of components during the routine use of the vehicle.
Onboard diagnosis usually differs from offboard diagnosis, which, in a known manner, is carried out by the repairer, preferably after having analyzed the onboard diagnosis, if necessary with the aid of a diagnostic aid device.
In particular this involves the repairer taking a decision on the strategy to adopt on the subject of a possible repair.
Generally, when a fault in the vehicle appears for the first time, the computer commands the recording of this event in a nonvolatile memory.
Usually, the event is associated in the memory with a code identifying the fault.
Therefore, on reading this memory, the diagnosis method is capable of recognizing the faulty component in the whole vehicle.
In the light of this diagnosis, if the danger that the fault represents for the vehicle and/or the passengers is great, the computer may if necessary command an emergency action (for example displaying a request for an emergency stop).
On the other hand, if the fault represents a slight danger, the computer does not usually initiate any action that is perceptible by the user until a garage repairman, analyzing the onboard diagnosis, identifies the fault and then repairs the component (offboard diagnosis).
One problem associated with this method is that the information given by the onboard diagnosis, the fault code in this instance, is relatively poor, which limits the quality of the offboard diagnosis and therefore the possibilities of action and/or reaction.
As an example, the onboard diagnosis is not able to differentiate between a permanent and an intermittent fault, that is to say that appears and then disappears at least once.
Consequently, such an information defect may limit the diagnosis of the repairer (offboard diagnosis) and therefore adversely affect the efficacy of his work.
In order to remedy these disadvantages, there is a known method in which the distance traveled at the time when the first event takes place is stored in addition to the fault code.
It will be noted here that in everyday language, the distance traveled corresponds to the mileage of the vehicle.
According to this method, it is possible to store the absolute mileage, or else the total mileage, that is to say the mileage read when the fault appears.
It may also store the relative mileage, namely the mileage read since said appearance.
In this respect, it is nowadays increasingly simple to obtain the absolute mileage of the vehicle.
Specifically, the computers of modern systems for monitoring a drive train usually use as a datum the instantaneous speed of the vehicle and reconstitute the absolute mileage by means of a time integration of this speed.
Having the absolute or relative mileage in the memory offers the advantage of increasing the quantity of information relating to the fault since the user also has a time-stamp of the appearance of this fault.
Although it has been of assistance on many occasions, such a method nevertheless remains limited.
In particular, the stored information is still insufficient when the user, as is increasingly the case, desires to enhance the quality of the diagnoses.
As an example, it may be of value to assess whether a fault that has finally disappeared has or could still cause other faults in the vehicle.
But, as will be understood, the method using the aforementioned simple time-stamp, and more generally the methods of the prior art, do not make it possible to generate any diagnosis on this subject.